Current collector



March 18, 1941. w SCHAAKE 2,235,387

CURRENT COLLECTOR Filed April 25, 1959 WITNESSES: INVENTOR 101M W/Y/I'am sc/m/fe V I Q.U-JiJ ;o-W BY I MW Patented Mar. 18, 1941 UNITED STATES PATENT OFFICE CURRENT COLLECTOR Pennsylvania Application April 25, 1939, Serial No. 269,891

Claims.

My invention relates, generally, tocurrent collectors, and in particular, to a slider shoe for collecting current from a trolley conductor.

In current collectors for collecting current from 5 an overhead conductor, it is generally desirable to provide a slider shoe that is both light in weight so that it may more readily follow irregularities in the conductor, and be maintained in contact therewith and which has durable wearing qualities so as not to require too frequent replacements. In order to protect trolley fixtures, such as frogs, crossings and the like, from undue damage as a result of impacts of the slider shoe therewith, it is preferable that the portions of the body of the slider shoe which most frequently come into contact with the overhead fixtures be of a relatively soft material. In order to prevent rapid wear of the slider shoe, the :portion of the slider shoe which engages the trolley conductor is preferably of a relatively hard material having durable wearing qualities.

Where separate wear inserts are used in connection with slider shoes of a relatively soft material to increase the life of the slider shoe,

' it is extremely difficult to secure good electrical contact between the wear insert, which forms a relatively large portion of the surface of the slider shoe in contact with the trolley conductor, and the body of the slider shoe without requiring accurate machining of the surfaces of the insert and the corresponding surfaces of the body member. Accordingly, it has been found desirable to construct the slider shoe by means of a casting process wherein the body member of the shoe is cast about a preformed wear insert so as to provide an integral construction.

The object of my invention, generally stated, is to provide a slider shoe for current collectors which is simple and inexpensive to manufacture, and which is durable and efiicient in operation.

A more specific object of my invention is to provide a slider shoe having a relatively soft body member with a hardened wear insert cast 5 integrally therewith which is heat treated after casting to produce the desired degree of hardness of the insert.

Another object of my invention is to provide A a construction for trolley shoes whereby a wear 6oinsert may be cast integrally with a body member of relatively soft material and the composite shoe subjected to a heat treatment to produce the necessary degree of hardness of the wear insert without impairing the body portion.

A further object of my invention is to provide for improving the wearing qualities of a hardened insert member in a slider shoe of a nonferrous metal after it has been cast integrally with the body portion of the shoe.

A still further object of my invention is to :5}

provide for casting a hardened insert member in an aluminum bronze alloy slider shoe body member and subsequently heat treating the slider shoe to increase the wearing qualities of the insert and normalize the body member. 10:

Another object of my invention is to provide an improved method of manufacture for composite slider shoes wherein a heat treatable wear insert is cast integrally with a relatively soft body member, and the slider shoe then subjected 151 to heat treatment to increase the hardness of the insert subsequent to the casting operation.

In practicing my invention, a heat treatable wear insert may be positioned in a mold and a body member of a relatively soft material capa- 2o ble of withstanding heat treatment cast thereabouts by pouring the molten metal, of which the body member is to be formed, in the mold. Subsequently, the slider shoe may be heat treated to improve the wearing qualities of the insert 25 member, so as to increase the life of the slider shoe.

For a more complete understanding of the nature and scope of my invention, reference may be had to the following detailed description taken 30 in connection with the accompanying drawing, in which Figure 1 is a side elevation view of a slider shoe embodying my invention; and

Fig. 2 is a sectional View of the slider shoe 35 of Figure 1 taken along the line II-II thereof.

Referring to Figs. 1 and 2 of the drawing, the reference numeral I0 designates, generally, the body member of a slider shoe for a current collector, which is formed of any suitable rela- 40 tively soft material so as to minimize the possibility of damage to trolley fixtures, such as frogs, crossings and the like, with which it comes into contact in its passage along the conductor. The material of the body member [0 preferably has 5 relatively high electrical conductivity and is capable of withstanding relatively high temperature heat treatment without impairment. The body member l0 may, for example, be formed of an aluminum bronze alloy containing from 7 50 to 9 percent aluminum, from to percent copper and from ,2.5 to 4 percent iron, which has been found to have excellent current collecting qualities, a high degree of resistance ,to corrosion, a relatively low coefiicient of friction, 55

and which may be subjected to relatively high temperature heat treatments, for a purpose which will hereinafter be explained in detail.

As illustrated, the body member ID is provided with a pair of upstanding lip l2 which define an elongated groove M on the upper side of the slider shoe for receiving a trolley wire IS. A downwardly projecting ear I8 is provided on the lower side of the slider shoewith an opening therein for receiving a suitable pin or shaft for securing the slider shoe to a pole head (not shown).

In order to prevent too rapid wear of the relatively soft body member 10 of the slider shoe,

a hardened insert member 22, of any suitable material which may be heat treated to secure the degree of hardness necessary to provide a 1 suitably long life to the slider shoe, is positioned therein so as to provide a hardened bearing surface in the groove I4 for engaging the conductor It. Any one of a number of suitable materials may be used for the insert member 22, such, for example, as a heat treatable cast iron, which has been graphitized by the addition of a silicide so as to produce a more uniform grain structure and permit hardening of the insert by subsequent heat treatment, so as to give a hardness of from 500 to 600 on the Brinell scale.

In constructing a slider shoe according to my invention, so as to secure a good electrical contact between the insert member 22 and the body member l0 of the slider shoe, the insert member 22 is preferably placed in the mold for the forming of the body member ID and the molten bronze aluminum alloy is poured therein. The molten metal flows close about the insert member and on solidifying, shrinks, so as to, in effect, form an integral union therewith, thus providing good electrical contact between the insert member 22 and the body member Ill.

To insure the insert member 22 having the necessary degree of hardness and the proper wearing qualities, so as to prevent undue friction and heating of the shoe in operation, the composite slider shoe is preferably subjected to heat treatment subsequent to casting so as to simultaneously increase the hardness of the insert member 22 and normalize the body member ID to remove any stresses produced therein by the shrinkage thereof during cooling, and improve the grain structure of both the insert and body member. For example, the slider shoe may be placed in a furnace and raised to a temperature of from 1580 to 1620 F. and held at that temperature for a suitable period. The slider shoe is then quenched in an oil bath, and subsequently reheated to a temperature of from 400 to 600 F., at which it is allowed to soak for a suitable time to thoroughly relieve any internal stresses and produce a desired grain structure in both the insert and the body member.

By this heat treatment subsequent to the casting operation, the hardness of the insert member 22 may be increased to a value of from 500 to 600 Brinell, as against a hardness of only from 250 to 300 Brinell immediately after the casting operation, irregardless of heat treatment of the insert prior to casting. The grain structure of both the insert member and the body member is also improved by the subsequent heat treatment, giving a greatly increased life .to the slider shoe and improving its current collecting characteristics.

From the above detailed description, taken in connection with the accompanying drawing it will be apparent that my invention provides a slider shoe for current collectors having heretofore unobtainable Wearing properties and which will not cause undue wear of the trolley fixtures in the overhead system. A slider shoe made ac.- cording to my invention is simple and inexpensive tomanufacture and may be readily manufactured on a production basis without requiring specialized treatment or intricate machining operations of any description.

Since certain changes may be made in the above description, and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matters contained in the description, or shown in the accompanying drawing shall be considered as'illustrative, and not in a limiting sense.

I claim as my invention:

1. A slider shoe for engaging a trolley conductor comprising, a cast body member of a relatively soft aluminum bronze alloy capable of withstanding heat treatment within a predetermined range of temperatures, and an insert of a relatively hard graphitized cast iron heat treatable at temperatures within the said range of temperatures to produce a predetermined hard- .ness in the insert cast integral within the body member so as to have one face exposed to provide a wear surface for engaging the conductor .and hardened after the casting operation by heat treatment including heating above a critical value for the insert which is within the said range of temperatures and quenching to improve its wear resisting qualities.

2. A slider shoe for engaging a trolley conductor comprising, a cast body member of a relatively soft aluminum bronze alloy that remains unaffected by predetermined temperatures and conditions, and a heat treatable wear insert of cast iron graphitized by introducing a silicide cast integral with the body member of a ferrous alloy capable of being hardened throughout after the casting operation by heat treatment including reheating after casting above the critical temperature of the insert and quenching under the predetermined temperatures and conditions.

3. A slider shoe for slidably engaging a trolley conductor comprising, a cast body member having a groove to receive the trolley conductor, the body member being of a relatively light and soft non-ferrous metal capable of withstanding being heated to -a predetermined temperature and quenched, and a hardened heat treatable graphitized cast iron insert cast integral with the body member to provide a wear resisting surface in the groove and rehardened throughout by heat ing the body member and insert to said predetermined temperature and quenching after the casting operation.

4. In a slider shoe for engaging a trolley conductor, in combination, a cast body member of a bronze aluminum alloy containing from 85 to 95 percent copper and from 7 to 9 per cent aluminum, and a heat treatable graphitized cast iron wear insert cast integral with the body member to provide a wear resisting surface for engaging the trolley conductor. and hardened by heat treatment including subjection to temperatures no higher than from 1500 to 1700 degrees F., followed by quenching and reheating to a draw temperature of from 400 to 600 degrees F., whereby the insert may be. hardened in position after the casting operation and the body member simultaneously normalized.

5. A slider rshoe'for engaging a trolley conened heat-treatable cast iron insert graphitized by the introduction of a silicide cast integral with the body member to provide a wear resisting surface for the groove capable of being hardened throughout after the casting operation by 5 said heat treatment.

WILLIAM SCHAAKE. 

